The production of the continuous basalt fiber (roving) currently is based on the use of the Pt-Rd bushings. The efficiency of continuous basalt fiber manufacturing using Pt-Rd bushing is about one order of magnitude times less than the production of boron silicate E-glass fiber also utilizing Pt-Rd bushings. The low efficiency of the continuous basalt fibers production (when compared to that of E-glass fiber) essentially limits their commercial compatibility, even the properties of basalt fiber in many aspects better than that of E-glass fibers. Two main factors limit the efficiency of continuous basalt fibers production:
a)—the temperature of fiberization of continuous basalt fiber (roving) is about 200-250 degree centigrade greater than that of borosilicate E-glass fiber (containing roughly 10% of boron oxide). The high temperature processing of basalt fiber production increases the Pt-Rd busing deterioration (creep, sag, etc.).b)—basalts by chemical composition present basic igneous rocks which containing the iron oxides in range of 7-15% (by mass).
The metallic iron reacts with platinum at the temperatures in range of 120° C., while the fiberization of continuous basalt fibers proceeds in range of 1260 C-1280 C.
The reaction of iron with platinum (Pt) proceeds via chemical reactive diffusion process. This process promotes the deterioration of platinum, reduces the term of Pt-Rd bushing operation. The losses of platinum in basalt fiber industry is essentially greater than that of Pt-Rd bushing used for E-glass fiber production
These factors provide negative impact on basalt fiber products cost. Even a one stage basalt fiber processing can be more economical than that of two stage E-glass fiber production. Basalt fiber manufacturing utilizing basalt rocks is one stage process. As opposed to basalt, E-glass fiber processing requires preliminary preparation of the raw material having predetermined chemical composition. The two stage E-glass fiber processing requires greater energy consumption than one stage process. However no yet bushings for basalt fiber roving are designed which operating as much long as Pt-Rd bushings for E-glass fiber industry. Because basalt—natural rock is tough material. Therefore the development of bushings capable operate at the temperatures greater than Pt-Rd bushings (1450 C) acute needed for production of continuous basalt fiber (roving). The alternatives to Pt-Rd bushings based on Fe—Cr-alloys are not perspective because the temperature operation of Fe—Cr-based alloys is even lower than that of bushings made from Pt-Rd-based alloys.
The current Pt-Rd bushings been in operation to manufacture basalt fiber roving usually consisting 200-400 orifices. While the E-glass fiber production is based on Pt-Rd bushings having 2000-4000 orifices. The matter of fact is that high melting point components are presented in basic igneous rocks are remaining not complete melted when the process proceeds at temperature 1450 C. Not complete melted high-melting point contaminants cause the orifices clogging, therefore the breakage of fiber filaments occurs when a stream of glass body is emitted from the orifices and then mechanically attenuated into continuous strand. Furthermore they appear centers of crystallization which provide negative impact on fiber properties. Especially ductile properties.
Apparently fiber become brittle due to presence of crystalline phase traces. Many failures occur between the bushing orificed withdraw plane and the applicator: U.S. Pat. Nos. 4,957,525; 4,886,535; 4,853,017. The past efforts to reduce breakage have emphasized the feed stock as the cause and the source of the cure. A large number of variables are presented in the art of a fiber forming process which tend to create a condition that encourages filament breakage in the fiber forming zone, see U.S. Pat. Nos. 5,312,470; 4,853,017; 4,676,813; 4,664,688; 4,488,891; 4,675,039; 4,469,499. Among other negative factor on fibers (filaments) formation is the presence of unacceptable heterogeneous glass body components containing highly stable aggregates of atoms referred to as “clusters”. The clusters appear as forerunners of nucleus of crystalline phases that cause a great percentage of the failures of continuous basalt fibers. This factor appears to be permanent when the natural rocks (basalts) are used as initial raw material to manufacture continuous fibers.
Previous Art for Making Fiber.
Numerous fiber manufacturing apparatus and methods have been disclosed in the U.S. Pat. Nos. 6,125,660; 6,044,666; 5,954,852; 5,876,529; 5,800,676; 5,614,132; 5,601, 628; 5,490,961; 5,458,822; 5,352,260; 5,312,470; 5,147,431; 5,134,179; 5,057,173; 4,964,891; 4,957,525; 4,950,355; 4,917750; 4,886,535; 4,853,017; 4,676,813; 4,664,688; 4,636,234; 4,534,177; 4,488,891 4,469,499; 4,437,869; 4,401,451; 4,398,933; 4,328,015; 4,199,336; 4,088,467; 4,009,015; 3,929,497; 3,854,986; 3,557,575; 3,475,147; 3,264,076; 3,048,640; 3,013,096.
The appearance of crystalline phase during fiberization can be significantly reduced if basalt glass body after homogenization at the temperature in range of 1450 C undergo additional heat-treatment at the temperature above 1450 C right before fiberization process. Important also increase the efficiency of mixing and the turbulence to flow of the melted basalt's. The good mixing provide positive impact on further stages of glass body preparation from the point of view of its homogeneity. The temperature operation of refractory materials of apparatus and ceramic bushing has to be great enough to maintain the temperature during additional heat-treatment after homogenization. It better decompose the high-melting point components in the area where from glass body is supplied to the orificed bushing discharge wall. The poor mixing and the hydrodynamic conditions of previously disclosed apparatuses do not allow complete decomposing of the high melting point contaminants. The not complete melted contaminants consisting the short range order of atoms (in range of elemental cells of crystalline structural state) tend to gather into the clusters. Even sub micron size clusters have the potential become the centers of crystallization during fiberization process. Even the traces of crystalline phase reduce the properties of fibers. The clusters tend to grow that cause the clogging of the orifices and the breakage of the continuous fiber.
The additional heat-treatment better provide inside of a ceramic bushing. This operation is disclosed in the U.S. Pat. No. 6,647,747. In accordance to U.S. Pat. No. 6,647,747 the ceramic bushing allows increase the temperature of basalt glass body to 1550 C inside of the upper chamber of a bushing. That is essentially greater than the average temperature of the homogenization which proceeds at 1450 C. The overheat treatment promotes to complete decomposing of the high melting point component are presented in the basic and intermediate (by SiO2 content) igneous rocks. The effectiveness of the heat-treatment of glass body inside of the bushing, however is reduced, if the distance from the upper chamber (where the heat-treatment operation is provided) and the discharge wall at the bottom of the lower chamber (where from a glass body is delivered to the orificed discharge wall) too big, and the temperature inside of the lower chamber of bushing is not well controlled—main disadvantages of U.S. Pat. No. 6,647,747.
In general approach the closer the heater to discharge wall the better the conditions to control the temperature of fiberization process. No such conditions, however, disclosed in the U.S. Pat. No. 6,647,747. The metallic bushings are disclosed in U.S. Pat. Nos. 6,044,666; 5,312,470; 5,147,431; 4,931,075; 4,957,525; 4,775,400; 4,676,813; 4,675,039; 4,664,688; 4,364,762; 4,343,637 etc. The orificed discharge wall is heated by low voltage current at thousand Amps. The electric heaters are applied for precision temperature control of discharge wall, including discharge wall of Pt-Rd bushings.
However all metallic bushing suffer limited temperature operation, which is commonly not enough great to complete decompose the high melting point components which are presented in most basic basalt rocks.
Therefore all apparatuses in mentioned patents (are disclosed before the U.S. Pat. No. 6,647,747) exhibit disadvantage as regarding limited capability to complete decomposing of high-melting point contaminants during homogenization. They all routinely exhibit lock mixing, poor turbulence during melting process and poor volatile elements degassing which is important when the natural material basalt rock is used. The bushings in mentioned above patents appear exhibit drawback of glass body mixing, poor turbulence to flow and as result not complete the volatile elements degassing. The predetermined chemical composition allows borosilicate fiber processing at the temperature below 1100 C. That is not allowed for basalt fiber manufacturing. That is why the apparatuses for manufacturing basalt fiber are designed different way than those applied for E-glass fiber manufacturing. The apparatuses are designed for manufacturing basalt fiber have to satisfy special requirements due to basalt rock properties. The apparatuses are designed to manufacture continuous borosilicate glass fibers are not require efficient mixing, turbulence to flow and degassing. Nevertheless numerous patents disclose the apparatuses for basalt fiber manufacturing are not too much differs from apparatuses applied for borosilicate E-glass fibers.
In summation the apparatus and the bushings are designed for manufacturing mineral (basalt) fibers in U.S. Pat. Nos. 6,044,666; 5,954,852; 5,954,852; 5,458,882; 5,312,470; 5,123,949; 4,149,866; 4,636,234; 4,853,017; 4,822,392; 4,775,400; 4,560,606; 4,488,891; 4,343,637 exhibit poor volatile elements degassing, low-efficient glass body mixing, poor turbulence to flow during basalt rock melting. The glass fiber processing is easier to run when compared to that of basalt fiber manufacturing. The glass body having predetermined composition requires simpler operations to accomplish homogenization process. It is not require the volatile elements degassing, glass body turbulence to flow, as much as basalt glass body does. Mentioned factors are not important for glass fiber processing as much as for fibers are produced from natural basalt rocks. Basalt rocks require efficient melting, mixing, degassing and complete decomposing of all high melting point components. Basalt fiber roving manufacturing is tough process.
Nevertheless the interest to basalt fiber manufacturing is steadily growing. Especially when the price of still rebar applied for reinforced concrete tends to grow constantly. The fibers made from basalt rocks exhibit many attractive properties for a variety of applications and especially for reinforced concrete applications, where the low cost E-glass fiber cannot be used because have not sufficient properties. E-glass fiber tends to deteriorate in the alkaline environment which is typical for cement based materials. It deteriorate even under solar ultraviolet exposure.
E-glass fiber contains a boron oxide from 8% to 12% (in mass) and the high diffusion mobility boron atoms (due to their small size) promotes deterioration glass fiber properties. especially when they are exposed to salt water or cement based alkaline environments. E-glass fibers also deteriorates when is subjected to the action of the outdoor freeze-thaw exposure. Basalt fiber, as opposed to E-glass fiber, has not boron oxide (B2O). The Mechanical Performance/Price Ratio of basalt fiber is greater than other fibers currently available on the market.
Both Russian and Ukrainian apparatus (5040472/33 (1994); 92310003 (92); 4766933/00-33 (2)2 (89); 4823441/00-33 (22) (90); 4861059/00-33 (22) (90); 4793760/00-33 (22) (90) including USSR patents (990697; 937358; 881009; 874673; 589215) including U.S. Pat. Nos. 6,044,666, 6,125,660 are referred to as similar to the present invention, because these apparatus/methods are designed to manufacture continuous fibers (roving) from the natural basalt rock materials. However the mentioned versions of apparatus are designed for industrial production of continuous basalt fiber (roving) are law efficient. The low efficiency of the basalt glass body preparation came from the apparatuses for manufacturing borosilicate fiber. Many features came from glass fiber industry to basalt fiber manufacturing without essential changing. The major problem of apparatuses designed for manufacturing glass fiber is their low-efficiency if they used to produce basalt fiber roving. Because poor mixing and not complete the high melting point complex oxides destruction/decomposing. All components of igneous rock have to be decomposed and the volatile components have to be degas from melted basalt.
Most apparatuses exhibit poor convection at the bottom, great gradient of basalt glass body viscosity at the depths chiefly due to the low heat transparent properties of basalt glass body, especially when gas heating is applied and gas burners are positioned on the top (on seal) of apparatus. The low infrared transparency of melted basalt causes a high gradient temperature and viscosity at the depths that significantly increases the time of uniform homogenization of basalt glass body. The convection and homogenization processes of basalt glass body are almost suppressed when the depth of bath is more than 50 millimeters (mm). The high viscosity causes the drawback of hydrodynamic characteristics at the depth greater 50 mm. The poor hydrodynamic characteristics are typical not only for bath type apparatus (discussed above), but also for horizontal apparatuses having straight stream basalt glass body to flow. It is reason why Russian/Ukrainian versions of horizontally extended apparatuses are designed to let basalt glass body to flow through horizontally extended zones having different depths Such horizontally extended apparatuses having zones with different depths are designed for basalt fiber roving manufacturing (Russian and Ukrainian versions). The temperature of melted basalt glass body in the apparatuses have been disclosed in the USSR Patent: 874673, CO3 B, 5/00.1981; Russian Patents, for example RU 2017691 C1, 30.04/92) drops at the depths at a rate in range of 5 degree centigrade per millimeter. The temperature gradient occurs due to a low infrared heat transparent property of the melted basalt glass body. The low heat transparency causes the crystallization at the bottom of apparatus. The viscosity of basalt glass body increases by depths dramatically if an additional heating is not provided. The accumulated high viscosity basalt glass body at the bottom of apparatus is named as “Harnisage” which means that basalt glass body flow in this layer is suppressed—almost “frozen”. In some patents this layer is considered useful because it accumulates high gravity contaminants preventing their entrance into bushing. However the accumulation of high gravity contaminants (which commonly appear high melting point metal oxides) is not endless process. Upon accumulation the high-melting/high gravity contaminants sooner or later lead to the orifices clogging if they do not outlet from the furnace. Therefore the breakage and the reduction of the mechanical properties of basalt fibers (lowering the strength and the flexible properties) becomes substantial for apparatuses having poor glass body mixing and homogenization.
The Method for Manufacturing
Mineral Fiber having bath type furnace to melt rock materials and the forehead to feeder is disclosed in the U.S. Pat. No. 6,125,660. The concept of improvement in this patent based on variation of depths of bath/forehead ratio is not enough efficient when basalt rock is used. These improvements cannot prevent the problems which inherent mentioned above FSU and Ukrainian/Russian apparatus are designed to manufacture basalt fiber: low efficiency of basalt rocks melting and poor turbulence of melted glass body flow. The forehead is an extension of bath type melting zone of apparatus. The typical “dead zone” exists between melting and forehead which tend to become zone of crystallization. The “dead zone” is a place where the glass body crystallization due to presence of forerunners—the nucleation of centers crystallization are substantially created. When glass body is delivered to forehead of the feeder the complex oxides clusters appear forerunners of centers of crystallization. The traces of crystalline phases make fibers brittle. Especially when the diameter greater 20 micrometers (μm). Eventually coarse basalt fiber at the diameters greater than 20 micrometers (μm) appear substantially brittle properties that limits their applications for Three-Dimension Fiber Reinforced Concrete (3D FRC).
The natural basalt rocks present the heterogeneous eutectic system containing a variety of complex oxides of high melting point components (abortive, forsterite, nepheline, quartzite, etc.).
Many previous efforts are related to the fiber breakage problem (U.S. Pat. Nos. 4,957,525; 4,886,535; 4,853,017) were focused on an external environment action: bad sizing, rough aprons, unacceptable fan tension, cooling system, humidity, operator and other factors rather than the fundamentals of fiber structure formation. The natural rocks (basalts) are containing high-gravity iron rich components which tend to accumulate at the bottom of the apparatus. The accumulation of iron rich contaminants causes the damage to the orificed bushing m because iron and platinum (Pt) are react each other. It is reason why the cathode-anode electrode heating to melt basalt rock melting is not recommended when Pt-Rd bushings are applied. The apparatuses and methods for forming mineral basalt fibers are presented in the U.S. Pat. Nos. 6,125,660; 6,044,666; 5,954,852; 5,895,715. The U.S. Pat. No. 6,044,666 discloses a fiber forming apparatus for a variety melt materials utilizing insulating flow through the different configuration of bores and the bushing blocks—block assembly.
A bushing block with one or more bores extending through a peripheral region thereof to divert a portion of a supply of molten fiberizable material from a central region of the bushing block to the peripheral region of the bushing block. This apparatus and method for forming fibers, however, exhibits poor volatile elements outlet during glass body distribution from the center to the peripheral bores of the bushing block. Therefore glass body turbulence inside of the bushing block bores is similar to that disclosed in U.S. Pat. No. 5,312,470. The plurality of bores (passage ways for glass body) extending through the bushing blocks are designed to produce generally continuous filaments from natural organic (non-glass substances) than from the rock minerals, in particular, natural basalt rock minerals. The system of blocks of bushing bores made of refractory materials are not designed for glass body mixing and turbulent to flow and therefore cannot be used to provide basalt glass body homogenization process.
The U.S. Pat. No. 5,954,852 discloses a method of making fiber using a cascade of rotors from the melts at a viscosity less than 18 poise (at 1400 C). The glass body is poured onto the top of rotor at a viscosity less than 10 poise, wherein the other rotors are positioned lower. This method is not designed to make continuous basalt fibers (even a mixture of basalt and diabase melt is mentioned in this patent). The U.S. Pat. No. 5,895,715 discloses a method (blasting process) of making shaped fibers from a variety of fiberizable melt materials including such as rock slag or basalt. However blasting process cannot be used to produce continuous basalt fiber (roving).
The U.S. Pat. No. 5,601,628 discloses method for production of mineral wool, particularly made of basalt melt which is fiberized by internal centrifuging in a spinner having a peripheral wall with a plurality of orifices. To produce mineral wool with good fiber fineness and largely free of unfiberized particles, the length of the filament cones and the configuration of the heated gas flows generated around the spinner are adjusted so that the majority of the filament cones emanating from the spinner orifices intersects the isotherm corresponding to viscosity of 100 poises. This enables the tips of the filament cones to reach into a cool zone, thereby increasing the viscosity at the tip of the filament cones to avoid breakage of the filament cones to be attenuated. The basaltic materials, either natural or modified basalts are available for production of rock wool. However this method is not available to produce continuous basalt fibers.
The ultra-high velocity water cooled cooper spinner method is applied to manufacture a non-continuous size mineral fibers (U.S. Pat. Nos. 4,468,931; 4,534,177) and a spinning formation fiber rotary methods (U.S. Pat. Nos. 4,724,668; 5,679,126; 4,917,725; 4,058,386) do not promote the production of continuous fiber with available properties. This method does not prevent the appearance of crystalline phase even at high speed rotations of spinner.
Previous Orificed Bushings Art Design
The industry of manufacturing glass fibers (including basalt fibers) for many years is used bushings made from precious metals such as platinum or platinum and rhodium (Pt-Rd) based alloys. These bushings, however, tend to creep or deform in service when applied to basalt fiber roving manufacturing due to high temperature fiberization in range of 1300 C. The creep or deformation adversely effects fiber quality. The deformation or “sag” requires the bushing to be prematurely removed from service. If corrosive affects don't take their toll on the bushing “sag” does. In addition, platinum reacts with iron is presented in basalts.
The bushings that have been disclosed at U.S. Pat. Nos. 6,044,66; 5,312,470; 5,147,431; 4,957,525; 4,853,017; 4,676,813; 4,664,688; 4,488,891; 4,469,499 typically include a bottom plate or wall, commonly referred to in art as a tip plate, which retains a pool of molten glass associated with the furnace. The Russian and Ukrainian versions of apparatus designed to manufacture basalt fiber locate the bushings separate (outside) separately from the main chamber where basalts melted and glass body homogenized. More specifically bushings are located underneath of the feeder's forehead.
The hydrostatic pressure of glass body in the feeders promotes molten glass to issue from the orifices of the bushing. However the hydrostatic pressure causes creep “sag” developing a curvature of the orificed plane (discharge wall) of the Pt-bushing at a temperature in range of 1300 C. As result the orificed plane of discharge wall becomes curved instead to be flat and such bushing has to be replaced (recycled).
The French Patent 1,116,519 discloses a bushing and a feeding source of molten glass combined with rotor equipped with a slop valve. The diameter of the filaments is modified by varying the speed of the rotor and its vertical position. The bushing base is generally “V”-shaped and has a series of parallel ‘V”-shaped elements, at the summit of each a row of orifices provided. This particular design and placing of the glass under pressure is proposed for the purpose of preventing flooding. Apparatus consisting a rotor in order to regulate the glass body flow in an effort to inhibit the flooding, but not prevents it completely. The U.S. Pat. Nos. 4,676,813; 4,675,039 discloses the method and apparatus for forming glass fiber. This invention provides the “drip less” type of feeder. This is accomplished by establishing a shallow layer of molten glass over an orificed discharge wall to provide the streams of molten glass for attenuation into filaments. The layer being maintained at a first level or depth to establish “non-drip less” operation to facilitate the restart of filament formation as desired.
Numerous efforts have been done in the past related to the improvement of orificed bushings. The U.S. Pat. No. 5,312,470 discloses apparatus—feeder or bushing for producing glass fiber where the heat transfer members or fin shields have outwardly disposed surfaces with a ceramic coating bonded to those surfaces. The heat transfer surfaces also are in direct contact with and adjacent to the discharge wall of the feeder where they act as support members to support the orificed discharge wall. This combination especially useful in designing feeders or bushings having a greater number of orifices.
However, the apparatus—bushing are disclosed in this patent exhibit limited temperature of homogenization which cannot be increased due to metallic discharge wall. These apparatus or bushing cannot be used to manufacture mineral (basalt) fibers from natural rocks containing a high melting point complex oxides.
The apparatus for forming glass fiber has been disclosed in the U.S. Pat. No. 5,312,470 presents an apparatus having feeder combined with discharge wall of a bushing, e.g., the bottom of a feeder is a discharge wall of a bushing containing plurality of orifices-tips. A such design of apparatus—feeder or bushing also cannot be used to manufacture mineral basalt fibers from natural rocks. It cannot sufficiently homogenize the glass body of basalt rocks. The bushing is disclosed in U.S. Pat. No. 4,957,525 also made out of precious Pt-Rd metals. The development of bushing is disclosed in the U.S. Pat. No. 5,147,431. However it uses precious Pt-Rd metals. The additional wall positioned above the orificed discharge wall is disclosed in the U.S. Pat. No. 4,676,813 made from platinum. Great efforts to improve bushings characteristics have been done in the U.S. Pat. Nos. 4,488,891; 4,437,869; 4,363,645. Some patents, for example, U.S. Pat. No. 5,312,417, disclose the coatings and junctions utilizing ceramic materials (such as yttrium stabilized zircon) which exhibit the thermal-shock resistance, but precious Pt metal is applied for the bushing.
In the U.S. Pat. No. 6,647,747 is disclosed ceramic bushing to manufacture continuous Mineral/basalt fibers. The external induction and or internal electrode heating systems are used to provide basalt glass body heating inside of upper chamber of ceramic bushing. The overheating to 1550 C requires materials having enhanced properties of the internal wall of a bushing. There is also problem to maintain 1450 C nearby the discharge wall made from ceramic orificed plates. The lower chamber of ceramic bushing is disclosed in U.S. Pat. No. 6,647,747 patent has not such heating system.
The permanent temperature gradient between the upper and the lower chamber in range of 150-250 degree centigrade is required for ceramic bushing to run fiberization process in range of 1260 C-1280 C.
The temperature gradient between the upper chamber and an orificed ceramic discharge wall depends not only from the temperature inside of upper chamber, but also from the thermally conductive properties of basalt glass body and an intermediate plate which divides the upper chamber from the lower chamber.
The external induction heating is not satisfy to the reliable temperature control nearby discharge wall which is located at the bottom of a bushing.
All together these factors do not allow maintain uniformity of the temperature in the area of discharge wall (U.S. Pat. No. 6,674,747).
The further development of apparatus integrated with ceramic bushings is proposed in this invention. The proposed invention discloses an apparatus which differs from those are described in previous patents (U.S. Pat. Nos. 6,647,747 and 6,125,660) by simplicity. The present invention discloses the ceramic bushing consisting discharge wall made from corrosion resistant ceramic materials such as: B4C, BN, Cr2O3—but not limited. Some of them consisting additives which thermodynamically increase the stability and the corrosion resistance of the ceramic materials in the melted basalt glass body environment.
To avoid melted basalt leak via gap between different parts of bushing (made from different ceramic materials), the adjusted gaps are filled out by the sealer-interface material having extremely high temperature melting point combined with plasticity properties, for example BN (white powder), or from the same chemical composition powder material. The ceramic bushing is made from plurality of orificed ceramic plates. Wherein the ceramic plates comprising a discharge wall functionality is to maintain the fiberization process-only. The temperature (1450 C-1550 C) of basalt glass body inside of the lower chamber of the bushing (above discharge wall) is achieved by using a heating element made from refractory electric conductive materials. For example, from Mo—molybdenum, MoSi2. Or from Cr—Fe-M; Cr—Mo-M; Cr—Ta-M; Cr—Re-M; Cr—Os-M-based alloys (where M—a metallic alloying element which is add. to reach the enhanced plasticity and the corrosion resistant properties). To produce such alloys the high-temperature powder sintering, D-Gun or arc plasma deposition technique is used rather than conventional metallurgical casting. These methods provide an important advantage versus conventional metallurgical process. Because not always possible produce chromium reach alloys (Cr-based alloys) with such refractory metals as: Mo, Re, Os etc. having melting points much greater than that of chromium (Cr). The melting point of chromium (Cr): Tm.p.=1863 C. In addition metallic chromium exhibit high partial pressure of vapor. Therefore Cr rather evaporated before the melting points of Mo, Re, Os will be achieved: 2623 C (Mo) to 3033 C (Os) and 3186 C (Re). Wherein the concentration of alloying elements for some parts of multi-sectional ceramic bushing should not exceed 20% (atomic percent).
The mentioned above Cr—Mo-M; Cr—Os-M; Cr—Re-M-based alloys commonly brittle. Nevertheless they can be prepared by not metallurgical casting process, because, for example heater in a shape of plate is not requires the precision machinery treatment during preparation. And it is not undergo to dynamic load action during operation. It just need to have high corrosion resistance property in basalt glass body, and alloy has to have the melting point greater than 1750 C. That is much greater than currently available Pt-Rd alloys and of course all Fe—Cr-based alloys, having melting points in range of 1450 C. The most of Fe—Cr-based alloys have been designed for orificed bushings exhibit the melting point even less than 1450 C.